In the field of cultural manuscripts, there is often a conflict between the preservation of an original manuscript and its complete study. For example, clay tablets were used in the Middle Bronze Age to communicate cuneiform messages. The clay tablets themselves were sometimes contained in a clay covering so that only the recipient could read the message, or they would at least know if someone else had read the message if the clay “envelope” was tampered with or missing.

Clay tablets with these envelopes survive to this day and are of great historical interest. However, reading the contents of a sealed “letter” and preserving the envelope can be difficult or impossible. By using X-rays, specifically computed tomography (CT), there is no need to compromise between these two goals.

The system was tested on a sample clay tablet that was created for that purpose. (Photo by Vanessa Tubiana-Brun, CNRS.)

Information as the Engine of All Research

Lennart Schulenburg, Managing Director of VisiConsult, said, “For most of our customers, the focus is on information about deviations and defects—such as in the field of aerospace where safety is an essential factor.” He adds that CT is increasingly being used in other application areas, such as the field of cultural manuscripts. Instead of revealing defects, here the focus is to use CT to nondestructively reveal information that can be used for important research.

Simply explained, the CT scan is performed using an X-ray source which penetrates the clay tablet. Depending on the material density, the beam is attenuated and is captured by a detector. During imaging, the clay tablet is automatically rotated 360°. From the numerous images, a digital 3D representation of the clay letter is created.

After evaluation, the 3D digital version of the letter can be examined as desired.

Examining Hidden Messages Nondestructively

After the images are processed, the hidden message is revealed on a computer monitor—the CT scan has made the cuneiform writing clearly legible.

One particular clay tablet dates back to the 19th century B.C. and comes from a private collection. The cuneiform text it contains represents one of the first references to the Assyrian written language. The text shows a message from two sisters to their brother. They chastise him for his greed for profit and neglect of his religious duties.

Professor Ralf Möller, Director of the Institute for Information Systems at the University of Lübeck, said, “This nondestructive method has proven to be excellent. On the monitor, you simply set a transparency for the envelope and you can see inside. The message becomes legible.”

As a result, information is gained and the discovery continues to be preserved.